Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: camperman on July 17, 2013, 01:16:57 PM

Title: VOX Mini 3.. No speaker output
Post by: camperman on July 17, 2013, 01:16:57 PM
I have a VOX Mini 3 which appears to be working perfectly through the headphones but is producing no output at the speaker.
The speaker is working fine and I've tried the obvious faulty contact in the headphones socket and but that's not the problem.

Does anyone have any suggestions of where to head next to find this fault please?

Thanks
Ed
Title: Re: VOX Mini 3.. No speaker output
Post by: Roly on July 18, 2013, 12:29:30 AM
Well if it's driving headphones okay, and the speaker tests okay, and the contacts aren't dirty, that just about leaves only one thing (since that socket is the only thing between the amp output and the speaker), a dry solder joint or crack on the printed circuit due to being wrenched at some stage (the headphone socket does mount directly on to the PCB, and there is no front panel retaining nut - right?  (how did I guess?)).

Wiggle the socket while looking at the solder side of the PCB, and it's Sydney to a brick you will see some movement in, or by, the solder joints and they need to be made good.

HTH
Title: Re: VOX Mini 3.. No speaker output
Post by: midibob on August 22, 2013, 03:26:55 AM
Hi Ed,

You will more than likely find the output chip has blown.
I've spent a lot of time on these amps and if you are interested follow this link :-

http://www.badcaps.net/forum/showthread.php?t=20949 (http://www.badcaps.net/forum/showthread.php?t=20949)

I have also developed a daughter board to enable a fairly easy repair.

Midibob
Title: Re: VOX Mini 3.. No speaker output
Post by: g1 on August 22, 2013, 08:15:52 PM
  That's quite something midibob, thanks for sharing!
How much do the daughterboards go for?
Title: Re: VOX Mini 3.. No speaker output
Post by: midibob on August 23, 2013, 09:09:25 AM
I'll PM you.

Midibob
Title: Re: VOX Mini 3.. No speaker output
Post by: g1 on August 23, 2013, 11:53:07 AM
  Thanks midibob!
For anyone needing to repair one of these, midibob's daughterboard is priced very reasonably.
  He doesn't want to list the price here in case it goes against forum advertising policy, but send him a PM if you need one.
Title: Re: VOX Mini 3.. No speaker output
Post by: joecool85 on August 27, 2013, 06:08:37 AM
Quote from: g1 on August 23, 2013, 11:53:07 AM
  Thanks midibob!
For anyone needing to repair one of these, midibob's daughterboard is priced very reasonably.
  He doesn't want to list the price here in case it goes against forum advertising policy, but send him a PM if you need one.

It does not go against forum policy so long as they aren't spamming the forum with ads etc, a simple mention of price is fine.
Title: Re: VOX Mini 3.. No speaker output
Post by: midibob on August 27, 2013, 03:19:26 PM
That's good to know.

If anyone is interested they are £10 each.
PM me if you want one.

Midibob
Title: Re: VOX Mini 3.. No speaker output
Post by: phaess on April 23, 2014, 09:55:42 AM
I received the daughter board from Midibob, installed it, and now the amp is good as new!
Title: Re: VOX Mini 3.. No speaker output
Post by: mattc_uk on June 13, 2021, 04:16:59 AM
We've got a VOX Mini 3 Gen 2, and it just gave up on any guitar output last night, just as my son was using it. Mic input works fine, but guitar input has failed completely.. no output in the headphone jack either. @midibob would your daughter board be able to fix this issue on the Gen 2, or am I looking at a new amp?  :-\
Title: Re: VOX Mini 3.. No speaker output
Post by: Jazz P Bass on June 13, 2021, 11:47:52 AM
It appears that you may have an Input Jack issue.
If the Mic Input works then the output stage is fine.
The 'daughter board' is meant to resolve an overall 'no output' issue. (blown output ic)
Title: Re: VOX Mini 3.. No speaker output
Post by: midibob on June 13, 2021, 03:32:26 PM
As Jazz P Bass says the output must be OK if the Mic is working.

For info I don't make these boards anymore but all the details are on Badcaps.net in the Forum for anyone wanting to make their own.
Title: Re: VOX Mini 3.. No speaker output
Post by: joecool85 on June 14, 2021, 04:21:48 PM
I had forgotten all about these.  Midibob, if you don't mind sharing a picture of the board and maybe some info, I'd love to have it here on this forum!
Title: Re: VOX Mini 3.. No speaker output
Post by: Jazz P Bass on June 14, 2021, 06:52:03 PM
The Vox amp uses the TPA3091 D1 ball grid array ic (cute!).
Midibob chose to use the SSM2305.
The layout that he chose is directly off of the datasheet.
https://www.badcaps.net/forum/showpost.php?p=350727&postcount=33
Title: Re: VOX Mini 3.. No speaker output
Post by: midibob on June 15, 2021, 08:59:18 AM
Here's a copy of the installation instructions but I must stress I don't make them anymore and don't have any!

Title: Re: VOX Mini 3.. No speaker output
Post by: Jazz P Bass on June 15, 2021, 11:42:49 AM
What in the heck were they thinking when they chose that IC ?>>>?
Great for a cell phone but a guitar amplifier?
Come on !
Good job midibob!!
Title: Re: VOX Mini 3.. No speaker output
Post by: midibob on June 15, 2021, 12:21:56 PM
Yep, my thoughts exactly. I did get some sample chips from Texas and replaced a couple but it was a hell of a job even with all my SMD stuff and a microscope. That's when I thought there must be an easier way. The icing on the cake was not having to remove the old chip. :dbtu:
Title: Re: VOX Mini 3.. No speaker output
Post by: joecool85 on June 15, 2021, 08:46:53 PM
Quote from: midibob on June 15, 2021, 08:59:18 AM
Here's a copy of the installation instructions but I must stress I don't make them anymore and don't have any!

Fantastic job, looks really professional!  No worries you don't make them anymore, still a very interesting share!
Title: Re: VOX Mini 3.. No speaker output
Post by: Jazz P Bass on June 16, 2021, 12:52:11 AM
To replace the ic properly the balls on the pcb have to be reflowed.
They make sheets of teflon with the correct spacing holes in them & you simply lay the sheet over the flattened balls apply flux and reflow the them.